Refrigeration system employing liquefied gas



Jan. 27, 1970 J. F. WATKINS 3,491,547

I REFRIGERATION SYSTEM EMPLOYING LIQUEF'IED GAS Filed Dec. 13, 1968 United States Patent U.S. Cl. 62217 9 Claims ABSTRACT OF THE DISCLOSURE A refrigeration system for cooling or air conditioning any volume or space, said system comprising a cold reservoir which releases a liquefied gas into a network of conduits wherein the liquefied gas is substantially vaporized in an evaporator and passed through either a first solenoid valve or a second solenoid valve and discharged through a conduit to the space to be refrigerated or discharged through a muffier to the atmosphere. In addition, dehumidifying units may be provided in the conduits to reduce moisture, and a means for ventilating the air across the evaporator is provided so that the refrigerated air may circulate.

This application is a continuation-in-part of a continuation-in-part application Ser. No. 638,824, filed May 16, 1967, and now abandoned.

This invention relates to improvements in a refrigeration system and more particularly, to improvements in a system for refrigerating or air conditioning any volume or space by vaporizing a liquefied gas at a controlled rate.

Accordingly, a primary object of this invention is an improved refrigeration system wherein a liquefied gas is converted to vapor at a controlled rate, and either discharged through a conduit to the space to be refrigerated or discharged through a muffler to the atmosphere.

A further object is an economical refrigeration or air conditioning system with an evaporator wherein the liquefied gas naturally expands thereby using less liquid gas and providing better cooling efliciency.

Another object is a reliable refrigeration or air conditioning system that includes an improved means for ventilating the air so that the refrigerated air may circulate.

FIGURE 1 is a diagrammatic view of the refrigeration system, and

FIGURE 2 is a diagrammatic view of another embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The refrigeration system 10 contains a reservoir of liquefied gas and a first network of conduits leading to an evaporator 12. In the evaporator 12 the liquefied gas expands, and is converted to vapor by atomization and absorption of heat from the space to be cooled. A second network of conduits leads out of the evaporator 12 to a means for regulating the flow of vaporized liquid. This means may consist of solenoid valves 14 and 16 which provide a complete temperature control of the space to be refrigerated.

From the means for regulating the flow of vaporized liquid the vapor may be discharged through either a conduit 20 to the space to be refrigerated or through a muffler 18 to the atmosphere. In addition, both networks of conduits may contain a dehumidifying unit 22 or 24 and relief valve 26 or 28 which operate respectively to reduce moisture and relieve excess pressure in the conduits.

The necessary refrigeration may be supplied by one or both of two alternative methods. One method consists of a means to draw air across the evaporator 12 thereby forcing cold air to circulate in the space to be refrigerated. The other method consists of releasing the vapor derived from the liquefied gas at a controlled rate within the space to be refrigerated.

The system is adaptable to a variety of uses, and may be used to refrigerate or air condition any volume or space. This system will provide the necessary degree of control both as to temperature of the volume or space to be refrigerated and as to use of the liquid refrigerant itself.

As shown in FIGURE 1, the refrigeration system 10 comprises a tank or container 30 which acts as a cold reservoir for a quantity of liquefied gas. The tank or container 30 may be any suitable vacuum type, and may be made from any suitable material such as metal. The cold reservoir stores the liquefied gas until needed, and is in communication with a fill pipe 32 in the first network of conduits. This fill pipe 32 may be operated by a hand valve or any other type of valve mechanism. Another conduit with a safety pop-01f valve, which is not shown, may be used as a tank exhaust means to relieve the tank or container 30 from excessive pressures.

As shown in FIGURE 1, the fill pipe 32 may lead to a dehumidifying unit 22 or similar means for reducing the amount of moisture in the conduits. The dehumidifying unit 22 is preferably an absorption type unit such as a silica gel dryer. The silica gel dryer absorbs excess moisture in the conduits, and reduces or eliminates moisture that would otherwise collect on the valves in the refrigeration system.

From the dehumidifying unit 22 another conduit or pipe 34 may lead to a relief valve or safety pop-off valve 26. Valve 26 is a pressure reducing valve for relieving the expansion chamber of excess pressure caused by expanding gas in the evaporator 12. Valve 26 is not related to the refrigeration aspects of the system and merely vents liquified gas to the atmosphere.

From the safety pop-off valve 26 a third conduit 36 leads to an evaporator 12. The evaporator 12 is preferably an expansion chamber having a plurality of horizontal tubes and a plurality of vertical fins with a header at each end of the horizontal tubes.

The evaporator 12 plays a very important role in the operation of this system. In the evaporator 12 the liquified gas naturally expands, and is converted to vapor by a process of atomization combined with the absorption of heat from the space to be cooled. The plurality of horizontal tubes and vertical fins reduce the liquid gas to a finer spray than when it entered the system from the cold reservoir thereby facilitating vaporization of the liquified gas. This feature combined with the fact that the evaporator 12 is at a higher temperature than the liquified gas when it entered the chamber, causes the refrigerant to vaporize. In addition, the size, shape and placement of the tubes and fins also helps produce optimum conditions during vaporization.

From the evaporator 12 the substantially vaporized refrigerant enters a conduit 38 in the second network of conduits. This conduit 38 may lead to a second relief valve or safety pop-off valve 28. Valve 28 another pressure reducing valve like valve 26. Although FIGURE 1 ,shows a .pressure reducin'g valve at each end of the evaporator 12 one such valve located at either end of the evaporator may be suificient to relieve the excess pressure iii the evaporator.

The second pop-off valve 28 communicates with another conduit 40 which may lead to another dehumidifying unit 24. As mentioned previously, the dehumidifying unit 24 preferably a silica gel dryer. It, along with the pop-off valve 28, may be located within either the first or second network of conduits or, as shown, may be located within both networks of conduits.

A third conduit 42 in the second network of conduits connects the silica gel dryer to another conduit 54 which leads 'to either the first solenoid valve 14 or the second solenoid valve 16. The first solenoid valve 14 is shown as thermostatically operated, but may be operated by any type of energy source.

The thermostat 44 and thermostat bulb 46 monitor the temperature of the evaporator 12 wherein the temperature of the evaporator is proportional to the temperature of the space to be refrigerated. The thermostat 44 may be set at any desired temperature, hoviever, for refrigeration purposes it is normally set at -40 F.

The thermostat 44 may be connected to a voltage source 48through an electrical connection or lead 50, and is shown in FIGURE 1 with the electrical positive lead 50 connecting the thermostat 44 to the power source 48. In addition an electrical negative lead 51 connectsthe first solenoid valve 14 to the power source 48.

The second solenoid valve 16 may be operated by a manual'single pole switch 56, and is connected to the 'power source 48 by an electrica l negative lead 60. A positive lead 52' 'leads from the thermostat 44 to both the first solenoid valve 14 and the second solenoid valve 16. It should also be pointed out thatthe two solenoid valves 14 and 16 provide an effective temperature control for the volume or space to be refrigerated.

When valve 14 is energized the vaporized refrigerant is released from the evaporator 12 and discharged to the space being refrigerated through conduit 20 allowing a new charge of liquid gas to enter the evaporator. When valve 16 is energized, the vaporized refrigerant is discharged to the atmosphere through an outside exhaust conduit 62 which may have a rnufiler 18. At no time does the refrigerant flow simultaneously through both valves 14 and 16, and muffler 18 has been added to merely re.- duce the noise of the escaping gas.

As with any refrigeration or air conditioning system, it is necessary to have a means for ventilating the air so that the refrigerated air may circulate. A ventilating fan 64 and motor 66 are preferably provided for this purpose, as shown in FIGURE 1. The ventilating fan 64 and motor 66 are used to draw air across the evaporator 12 thereby circulating cold air within the space to be refrigerated.

As shown in FIGURE 1, the blower fan 64 has an electrical positive lead 68 connected to the power source 48 and an electrical negative lead 70 connected to the first solenoid valve 14. However, it should be noted that the ventilating fan 64 may be driven by any power or energy source and may, for instance, be cryogenically driven.

When the vapor is discharged into the space to be refrigerated, it may then be circulated by the blower fan 64. This provides a suitable circulation means by forcing a flow of air across the evaporator 12 which is cooled by the liquefied gas. As the temperature of the space to be refrigerated drops and the temperature of the evaporator 12 drops in accordance therewith, the thermostat 44 will open at a predetermined temperature to close the solenoid valves 14 and '16. This is the temperature at which sufiicient cooling is provided so that the a ditional temp rature drop s d sired. However,

it is often important to maintain circulation of the air within the space to be cooled, and thus the blower fan 64 may continue to run even though the system has tempgrarily stopped discharging the vapor to the space to be refrigerated. 1 r I FIGURE 2 shows another embodiment of this invention. In this embodiment two refrigeration units are joined or tied together forming a dual refrigeration system 110. The two units are also interconnected through a relay system so that when one unit fails or is shutoff, the other unit may be actuated.

Each unit in the dual system is substantially similar to the single system shown in FIGURE 1, and contains a source of liquified gas 130, a first network of conduits 111, an evaporator 112, a secondnetwork of conduits 113, a first solenoid valve 114 and a second solenoid valve 116.

Each evaporator 112 operates in the same mariner as described for FIGURE 1 and, preferably, is an expansion chamber with a plurality of horizontal tubes and a plurality of vertical fins having a header at each end of the horizontal tubes.

As described for FIGURE 1, dehumidifying units 122 and 124 and pop otf valves 126 and 128 may be mounted within either the first or second network of conduits or, as shown, within both networks of conduits.

When either solenoid valve 114 is energized the vaporized refrigerant is discharged through respective conduits to the space to be refrigerated. When it is desired to discharge the vaporized refrigerant of either unit to the atmosphere through outside conduits and mufflers 118, either valve 116 may be energized.

The ventilating fans 125, 127 and 129 and motors 166 are shown in their preferred form in the dual system, and may be 'arranged such that the fans and 127 blow air across the evaporators 112 while tems 129 pull air across the evaporators.

The dual system has two common leads 121 and 123 connected to an electrical power source 148 with the remaining electrical leads the same as shown in FIGURE 1. It is also important to note that although this embodiment is shown as containing two refrigeration units it may contain any desired number of units.

The use, operation and function of this invention are as follows:

As previously mentioned, a tank or container 30 or 130 acts as a cold reservoir for a quantity of liquefied gas which may be either pumped or released into the refrigeration system through a fill pipe 32 or 132. The liquefied gas may then pass through a dehumidifying unit 22 or 122, such as a silica gel dryer, wherein the excess moisture in the conduits is removed. From the dehumidifying unit 22 or 122 the liquefied gas may pass through a relief valve 26 or 126. From the relief valve 26 or 126 the liquefied gas passes through another conduit 36 or 136 leading to an evaporator 12 or 112. In the evaporator the liquefied gas expands and is substantially vaporized by a process of atomization and absorption of heat.

After the liquefied gas is substantially vaporized it may again pass through a relief valve 28 or 128 and dehumidifying unit 24 or 124. From here the vaporized liquid enters either the first solenoid valve 14 or 114, or the second solenoid valve 16 or 116, depending on which valve is energized.

The solenoid valves prevent excessive amounts of liquefied gas from being used and wasted in addition to providing a complete temperature control and regulation. The first solenoid valve 14 or 114 is preferably operated by setting a thermostat 44 or 144 at the desired temperature. The second solenoid valve 16 or 116 is preferably operated by a manual single pole switch 56 or 156.

From either the first solenoid valve 14 or 114, or the second solenoid valve 16 or 116, the gas may be exhausted or discharged through either a conduit 20 or 120 to the space being refrigerated or, if desired, through a conduit and muflier 18 or 118 to the atmosphere. The

refrigerant is exhausted to the space being refrigerated so that the temperature will drop much faster in the'space being refrigerated. This will also lower the oxygen content of the air to prevent spoiling of produce such as vegetables and fruit.

In addition, a means to circulate the refrigerated air across the evaporator 12 or 112 and into the space to be refrigerated is preferably provided. This means is shown in the figures as blower or ventilating fans 64, 125, 127 and 129 which are situated to cause an effective flow of air across the evaporator and within the space to be refrigerated.

It is important to note that the dual refrigeration system 110, shown in FIGURE 2, may be used in a trucking unit and provides continuous refrigeration even if one unit fails. If failure or stoppage occurs for some reason, then the other unit may be actuated through use of a relay system.

It has been found that liquid nitrogen is one of the best liquid gases to be used as a refrigerant or cooling agent because of its commercial availability at a low cost and its large gas to liquid expansion ratio. In addition, it has the advantage of an extremely low temperature of approximately 320 F. in the liquid state. a

If liquid nitrogen is used in this system, the temperature of the nitrogen as it enters the evaporator 12 or 112 is approximately -320 F., however, as it passes from the evaporator to the solenoid valves 14 or 114 and 16 or 116, the temperature rises to approximately 72 F. As previously mentioned, the thermostat 44 or 144 whlch regulates the temperature at the first solenoid valve is normally set at 40 F. for refrigeration. The volume or space being refrigerated is, of course, at a hlgher temperature than -40 F.

In addition, it is important to note that although this invention has been shown as electrically driven, it may also be driven by any type of energy source such as hydraulic or cryogenic.

I claim:

1. A refrigeration system for regulating the temperature of any volume or space by vaporizing a liquified gas at a controlled rate, said system including:

a source of liquefied gas,

evaporator means wherein said liquefied gas expands and is converted to vapor by atomization and absorption of heat,

means for regulating the flow of vaporized liquid to provide a complete temperature control of the space being refrigerated,

a first network of conduits for conveying the liquefied gas from said source to said evaporator means,

a second network of conduits for conveying the vaporized liquid from said evaporator means to said means for regulating the flow of vaporized liquid,

means for reducing moisture in said conduits,

valve means to exhaust liquefied gas and relieve the system of excess pressure,

means for ventilating air across said evaporator means so that the refrigerated air may circulate, and

exhaust means including means to discharge the vaporized liquid to the space being refrigerated.

2. The refrigeration system of claim 1 further characterized in that the liquefied gas is contained in a tank until needed, and further, the supply of liquefied gas is regulated by a valve mechanism controlling the amount of liquefied gas that enters the system.

3. The refrigeration system of claim 1 further characterized in that the evaporator means is an expansion chamber having a plurality of horizontal tubes and a plurality of vertical fins with a header at each end of the horizontal tubes.

4. The refrigeration system of claim 1 further characterized in that the means for reducing moisture in the conduits consists of at least one silica gel dryer.

5. The refrigeration system of claim 1 further characterized in that the means for ventilating air across the evaporator means includes at least one. ventilating fan with an energy source for circulating cold air within the space being refrigerated.

6. The refrigeration system of claim 1 further characterized in that the exhaust means includes a conduit and muffier to discharge the vaporized liquid to the atmosphere.

7. The refrigeration system of claim 1 further characterized in that the means for regulating the flow of vaporized liquid includes a first solenoid valve and a second solenoid valve, said second solenoid valve having a manual by-pass switch, and said first and second solenoid valves being operated by a thermostat, whereby the temperature of the evaporator means is monitored and temperature control for the space being refrigerated is provided.

8. The refrigeration system of claim 1 further characterized in that the means for reducing moisture in the conduits includes at least two silica gel dryers, one of which is located within said first network of conduits, and the other of which is located within said second network of conduits.

9. The refrigeration system of claim 1 wherein at least two separate refrigeration units are interconnected.

References Cited UNITED STATES PATENTS 2,198,258 4/1940 Money 62296 2,279,928 4/ 1942 Shoemaker 62474 XR 2,496,816 2/1950 Schlumbohm 62514 XR 2,925,722 2/ 1960 Blackburn 625 14 XR 3,092,977 6/ 1963 Skinner 62217 XR 3,293,877 12/1966 Barnes 62514 XR MEYER PERLIN, Primary Examiner US. Cl. X.R. 62474, 514 

